Notes to broadcasters
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Farmers need to assess at what point spending money on pest control is justified. If a farmer spends money on a pesticide to control pests that are only doing a small amount of damage, he or she may actually lose money. To minimize damage, farmers should examine their fields regularly to monitor pest population levels, and apply controls only when infestations reach a level of ‘economic damage.’ Economic damage is the point at which the loss of income from the damaged crop is greater than the cost of buying and applying a pesticide.
The following script shows that pesticides or other pest control methods may not be necessary if the damage caused to crops is minimal. You may want to talk to an agricultural extension worker to find out what the economic damage levels are for commonly grown crops in your region, and include this information in your broadcast. This will help the farmers in your listening audience to better understand the concept of economic damage. For example, farmers in Guatemala learned how to test for economic damage levels in stored beans. They were taught to check samples of stored beans every 30 days to look for weevil damage. If more than four out of every 100 beans (4%) were damaged, the farmers were advised to control the pest. If the percentage of damaged seed was less than four percent, there would not be a significant reduction in germination, nutritional quality or sale price of the beans.
Good day and welcome to the program. In our discussion today, we’re going to talk about controlling pests in your crops. Let’s keep these two questions in mind: When should a farmer use pest controls? In fact, is it always necessary to control pests – especially if there are just a few insects eating your crop? This should be an interesting discussion… please stay tuned.
MUSICAL INTERLUDE (3 seconds).
Some farmers think only bad thoughts when they hear the buzzing sound of an insect around their crops.
And why not? Those buzzing insects are pests!
Are they? Is it true that an insect is always a pest?
Well, the obvious answer to that question is… yes! I think any insect that eats my crops is a pest.
Well – I disagree with you. I see it differently. I suggest to you that an insect becomes a pest only when it damages enough of your crop to make you lose money. And at that point, that’s when you need to think about how to control it.
I’m not sure I agree with you. If I see whiteflies on my cabbage I want to stop them from eating my crop immediately! I don’t have time to wait and figure out how much damage they’ve done!
Well, look at it this way. How many cabbages are the whiteflies eating? Let’s say they eat three cabbages. Imagine that these three cabbages are worth one dollar [insert local currency amount] in the market. So the insects are eating one dollar [insert local currency amount] of your profit.
But I don’t want to lose any of my profit.
Of course not. But if they are eating one dollar of your profit, it doesn’t make sense to spend more than one dollar to control them. If it costs you two dollars to spray chemicals on the cabbages, then you are spending two dollars to stop the insects from eating three cabbages that are worth a total of one dollar. So you would actually lose money.
So what you’re saying is that I lose money by spraying the pest. Hmmmm. I certainly don’t want to lose money on my crops!
All I’m saying is that you don’t have to panic when you first see the insects.
Right. I shouldn’t panic and think I have to spray as soon as I see some insects around my crops.
So now we have another way of thinking about insects and pests. An insect is a pest when the amount of damage it does to your plants justifies spending money to control it.
FADE IN MUSIC AND HOLD UNDER NARRATION.
Remember farmers: there must be a certain number of insects, causing a certain amount of damage, before they become a real problem. Check the amount of damage the insects are doing and decide whether or not it makes sense to spend money to control them. It may not be too serious if you harvest a few damaged cabbages; if they are too damaged for market, you can always keep them for your family to eat.
FADE OUT MUSIC.
- Contributed by Jennifer Pittet, researcher/writer, Thornbury, Ontario, Canada.
- Adapted from Developing Countries Farm Radio Network Package 28, number 4, Is an insect always a pest?
- Reviewed by Hélène Chiasson, PhD, Codena inc., Saint-Charles-sur-Richelieu, Québec, Canada.
- Course on integrated pest management presented by Hermogenes Castillo, ALTERTEC, Guatemala, 1992.
- Rappaport, Rosalyn. Controlling crop pests and diseases. Macmillan Press 1992. Tropical agricultural extension handbooks.